Mosquito host-seeking behavior is not well understood. The cues used by mosquitoes to locate hosts and the flight behaviors involved in finding those cues remain obscure. The fact that many human pathogens are carried and transmitted by mosquitoes makes understanding their basic biology essential, especially now that the classical control methods seem to be failing worldwide. The studies proposed here will attempt to uncover some of the basic underlying mechanisms associated with mosquito host-seeking and general flight behavior. Results will help to improve our understanding of disease transmission and our capacity to control mosquitoes. An interspecific comparison and evaluation of mosquito flight behavior is proposed. The host-seeking, dispersal, and blood-feeding behaviors of several important vector and pest mosquito species will be evaluated with a large (11 X 2.4 X 2.4 meters) outdoor wind tunnel which has been build and tested. This unique, automated tunnel is designed as an olfactometer with a pair of choice chambers upwind of the mosquito release point. Individual, multiple or competing stimuli (i.e., visual, auditory, olfactory) can be presented (simultaneously) and their importance to mosquito orientation and host-seeking flight behavior evaluated based on the comparative response of mosquitoes to each. We plan to compare the behaviors of day-active vs. crepuscular/nocturnally-active mosquitoes, the flight behavior of colonized, F1, and wild mosquitoes of the same species and the flight behavior of marked (i.e., with fluorescent powder) and unmarked mosquitoes. We also will investigate the phenomenon of host preference and attempt to determine the behavioral basis behind the observed feeding patterns of several mosquito species in the field. Finally, with this wind tunnel system we will be able to evaluate field-observed mosquito behaviors in a more controlled setting. For example, we will attempt to determine the reasons behind our recent observation that lard-can traps with accessible hosts, upon which trapped mosquitoes can blood-feed, capture up to 10 times the number of mosquitoes as traps with inaccessible hosts, on which mosquitoes cannot make contact or feed.